UPDATE 1-U.S. FCC votes to restrict AT&T, Verizon in 2015 spectrum auction

(Adds quote from FCC chairman, spectrum screen vote results and background)

May 15 (Reuters) - U.S. telecom regulators on Thursday voted to limit how much spectrum Verizon Communications Inc and AT&T Inc will be able to buy in next year's auction of highly valuable wireless airwaves.

In a 3-2 vote along party lines, the Federal Communications Commission approved the plan that would reserve part of the spectrum in each market for wireless carriers that do not already have substantial blocks of low-frequency airwaves there, largely restricting Verizon and AT&T participation.

"What this rule does is prevent those with current low-band spectrum from monopolizing the market in the auction by assuring that some spectrum will be available for those with insufficient amounts of spectrum to serve rural areas and penetrate buildings," said FCC Chairman Tom Wheeler

The FCC also voted 3-2 to expand the so-called spectrum screen, a calculation of what airwaves are usable for wireless, to include more of the airwaves currently controlled by Sprint Corp and Dish Network Corp, among other things.

The FCC has scheduled a major auction of low-frequency spectrum for mid-2015, a first opportunity in years for wireless carriers to buy the airwaves considered the beach-front property of radio spectrum for their reach and strength.

Smaller national carriers Sprint Corp and T-Mobile USA Inc had urged the FCC to ensure their two biggest rivals do not dominate the auction and FCC Chairman Tom Wheeler has agreed, saying Verizon and AT&T already control almost two-thirds of the coveted low-frequency airwaves.

(Reporting by Alina Selyukh and Marina Lopes; Editing by Chris Reese and Andrew Hay)